# B Can gravitational waves interfere with each other?

#### stefan r

Gold Member
And tides also distort spheres into ellipsoids. Correct?
Slightly ovoid. But I think it is fine to think of both tides and rotation as creating an oblate spheroid. A spheroid is a special case of ellipsoid where 2 axis are equal.

My impression is that the gravity wave does not create an oblate spheroid. Starting with a perfect sphere 2 of the axes change in opposite ways. So 3 equal diameters become 3 non equal lengths.

Might be worth pointing out that tides are different from wind wave height. Something well above high water could get wet. Tidal waves and storm surges are also different.

#### stefan r

Gold Member
The difference between 10^-12 and 10-21 is a billion to one, so assuming things being equal, the gravity wave would have to be at least one billion times stronger to be heard. I think if you actually were close enough to say a binary black hole to hear it you would be in deep doo doo.
Anyone close to a black hole is in deep. The wave would be minimal concern.

An oil tanker (or kayak) on the open ocean can get hit by a tsunami without the crew noticing. Same tsunami can destroy coastal civilization hundreds of kilometers away. Boats do not sink even if the swell is higher than the deck.

Your ear drum and all of the fluids that it contacts are inside the same wave. There is nothing to hear.

#### snorkack

The difference between 10^-12 and 10-21 is a billion to one, so assuming things being equal, the gravity wave would have to be at least one billion times stronger to be heard. I think if you actually were close enough to say a binary black hole to hear it you would be in deep doo doo.
You are not in deep doo doo when you hear 0 dB sound. You do have some discomfort and hearing problems when you hear 120 dB sound, but it´s still not immediately fatal.
The source of 10-21 amplitude gravitational wave was estimated to be 109 lightyears away. So a gravitational wave might have an amplitude of 10-12 when the source is a lightyear away.
If a 60 solar mass black hole were to fly by Solar System at a distance of 1 lightyear, at a relative speed of 200 km/s, what effects are to be expected on Solar System?

#### mfb

Mentor
If there is no matter falling in, we would just note the gravitational lensing effect on starlight passing close to it, most notably in Gaia data.

#### stefan r

Gold Member
If a 60 solar mass black hole were to fly by Solar System at a distance of 1 lightyear, at a relative speed of 200 km/s, what effects are to be expected on Solar System?
Can we change that to "minimum distance". 300 km/s is easier if you calculate in your head, 0.1% light speed. 1000 years to go from 1.414 light years to 1 light year.
Not much recognizable change to earth orbit because the pass is a few thousand years. The path of the sun-earth barycenter shifts toward the black hole.
If the black hole was 64 solar masses then an Oort cloud object at 1/8th light year would feel equal gravity, the orbit changes a lot. A comet with an orbit not parallel to the black hole would shift orbital planes. You would have to calculate the effect for each orbit and the timing. Some of the comets will fly through the inner solar system. Some get captured by Jupiter and become regular comets. Kuiper belt objects shift a little. Some Kuiper objects could interact with each other but it is also possible that objects would have interacted but now they do not.
The heliopause and termination shock would move further from the sun in the direction of the black hole.

#### snorkack

If there is no matter falling in, we would just note the gravitational lensing effect on starlight passing close to it, most notably in Gaia data.
The heliopause and termination shock would move further from the sun in the direction of the black hole.
Why in that direction?
There would be some matter falling in. The sparse interstellar gas of Local Bubble.
But if you have a black hole moving at high relative speed through sparse interstellar gas, what kind of disturbance is created? The gas accelerates on approach to the hole - then falls past event horizon with most of its kinetic energy.

"Can gravitational waves interfere with each other?"

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